The present invention relates to a coated polymer substrate.
Polymers are used extensively to make a variety of products which include blown and cast films, extruded sheets, injection molded articles, foams, blow molded articles, extruded pipe, monofilaments, and nonwoven webs. Some of such polymers, such as polyolefins, are naturally hydrophobic, and for many uses this property is either a positive attribute or at least not a disadvantage.
There are a number of uses for polymers, however, where their hydrophobic nature either limits their usefulness or requires some effort to modify the surface characteristics of the shaped articles made therefrom. By way of example, polyolefins, such as polyethylene and polypropylene, are used to manufacture polymeric fabrics which are employed in the construction of such disposable absorbent articles as diapers, feminine care products, incontinence products, training pants, wipes, and the like. Such polymeric fabrics often are nonwoven webs prepared by, for example, such processes as meltblowing, coforming, and spunbonding. Frequently, such polymeric fabrics need to be wettable by water or aqueous-based liquids. Wettability can be obtained by spraying or otherwise coating (i.e., surface treating or topically treating) the fabric with a surfactant solution during or after its formation, and then drying the web.
Some of the more common topically applied surfactants are nonionic surfactants, such as polyethoxylated octylphenols and condensation products of propylene oxide with propylene glycol, by way of illustration only. These surfactants are effective in rendering normally hydrophobic polymeric fabrics water wettable. However, the surfactant is readily removed from the fabric, often after only a single exposure to an aqueous liquid. Such surfactants are effective in rendering the hydrophobic polymeric fabric wettable by lowering the surface tension of the aqueous liquid. Such a mechanism must involve at least partial removal of surfactant from the surfaces of the fibers of which the fabric is composed.
Accordingly, there is a need for a coated porous hydrophobic substrate having a durable coating which is wettable by water without significantly lowering the surface tension of an aqueous medium to which the coated substrate may be exposed.